1. Field of the Invention
The present application relates generally to methods and compounds for forming thin films comprising gallium nitride (GaN) by atomic layer deposition. Such films may find use, for example, in optoelectronic applications, such as light emitting diodes (LEDs).
2. Description of the Related Art
Currently several issues plague the manufacturing of GaN-based LEDs: poor yield of devices producing the desired wavelength and subsequent need for cumbersome device sorting, and decreasing revenue per substrate (the price ratio of LEDs producing the desired wavelength and ones with a slight deviation from this wavelength is roughly 500:1). Currently an InGaN/GaN multi-quantum well (MQW) structure in HB-LEDs is deposited by MOCVD and the deposition involves thermal cycling between approximately 700° C. and 950° C. The high temperature used limits, due to diffusion, the maximum indium concentration in the InGaN; in practice the indium concentration is limited roughly to 20 atom-% before significant diffusion of indium occurs. Additionally, in the MOCVD deposited HBLED, small variations in the deposition temperature inside the substrate area lead to minute changes in indium concentration in the InGaN layer and, subsequently, a change in the emission wavelength, leading to poor yield due to poor indium uniformity in indium content in InGaN. MOCVD also has limitations in maximum obtainable indium concentration in InGaN, limited earlier by increased mobility due to thermal cycling thermal budget, and temperature uniformity requirements.
A need exists, therefore, for methods for controllably and reliably forming thin films comprising GaN by ALD.